1. Field of the Invention:
The invention relates to a prosthesis device for the patello-femoral joint.
2. Description of the Prior Art:
Patello-femoral prostheses are known which are used to replace the articulating surfaces of the patello-fermoral joint.
U.S. Pat. No. 3,878,566 discloses such a device comprising a femoral prosthesis which is attached to the femur and a patellar prosthesis which is secured to the patella. The patellar prosthesis has a ridge which slidably moves within a trough-like indentation in the femoral prosthesis.
Other patents disclose various other types of prostheses which are similar in their structure and operation.
In all of the prior art devices there is nothing to prevent the component prostheses from coming apart from each other in use. If the ridge moves out of the indentation, the prostheses may be displaced laterally or medially with respect to each other, which is extremely undesirable.